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50                                             ANILINE

8.  Benzene and Mineral Oils.— 2-3 c.c. are shaken in a test-tube
with as much pure sulphuric acid (66° Baume) ;   after 5-10 minutes the
appearance of a turbidity indicates benzene or the separation at the surface
of drops or a liquid layer, mineral oils.

9.  Determination of the Amyl Acetate.—This is effected by means
of the saponification number, proceeding as with essential oils (q.v.).    The
saponification number of pure4 amyl acetate is 431 ;   i part of KOH =
2-3169 parts of C5HH-(\H/X.

Ethyl propyl and butyl acetates, having the respective saponification
indices, 636, 549 and 483 raise that of amyl acetate whilst alcohols (amyl,
ethyl), acetone, benzene and mineral oils lower it.

Commercial amyl acetate almost always contains a certain proportion of
free amyl alcohol. It may be regarded as technically pure (e.g., when required
for photometric purposes) when it has 1) - 0-872 -<>'<S7(», distils to the extent
of 90% between 137° and i.|.}n, has a saponification number of about .j^o, is
neutral and leaves no oily spot on filter-paper.

ANILINE
C6H6-NHa==93

Various qualities of aniline are, found on the market : Pure aniline
(aniline oil for blue), a colourless or yellowish liquid which readily turns
brown in the air and light, and has an aromatic odour. Aniline' oils (crude
anilines], mixtures of aniline with, ortho- and para-toluidines, form reddish-
brown liquids of unpleasant odour. Aniline oil for red contains about equal
proportions of aniline, ortho- and para-toluidine, and aniline oil for sufraninc
about 40% of aniline and (>o% of orthotoluidine. Liquid loluidim is a
mixture of ortho- and pani-toluidines with a little aniline.

1.   Aniline

With aniline, besides determinations of the specific gravity and boiling
point by the ordinary methods, the. following tests arc made :

1.  Non-basic Substances.--10 c.c. should give a. quite clear solution
with 50 c.c. of water and 40 c.c:. of hydrochloric acid ;   incomplete solution
indicates the presence of hydrocarbons and nitrobenzene.

2.  Moisture.—loo c.c. are distilled, the. first 10 c.e. of distillate being
collected in a graduated 15 c.c. cylinder and shaken with 1 c.c. of saturated
sodium chloride solution and any diminution in its volume noted.

3.  Sulphur.—loo c.c. are boiled for some time in a redux apparatus
(the sulphur being transformed into hydrogen sulphide) and a current of
carbon dioxide then passed through the aniline into silver nitrate solution ;
a black precipitate in the latter indicates that the aniline contains sulphur.
This test is quantitative when standard silver nitrate solution is used and
the titrc determined after removal of the sulphide, by filtration,

4.  Determination of the Aniline,—If the preceding tests indicate
that the aniline is not pure, the aniline may be determined by the method
described below for aniline oils.

Pure aniline has I) 1-0267 at 15° and b.pt, 184°.   The commercial pure pro-the determination of the; alcohol. The alcohol by volume multiplied